[MidnightMoon]

Hello yalls, so I have a problem with my 1997 F250 HD 7.3L Powerstroke. I have a hard brake pedal on it. I replaced the brake booster as I thought that's what it was but it wasn't. I do have vacuum at the check valve so my vacuum pump is working. I do have the light on on the dash. My brakes get one good pedal push where it is soft but if I let off and push them again it gets hard. The booster came with a new check valve so I know that's not it. I am thinking it is a vacuum leak because I can not change what vent the air comes out either. Have any of you guys had this problem or maybe have a diagram of how the vacuum lines are ran. I work at a ford dealership and the workshop Manuel will not give me a diagram of the vacuum lines only for electrical. Any advice?

 

[Bugman]

It's either a vacuum leak or the pump. You really need a gauge to tell if it is good or not.

You can also block off the ports on the vacuum manifold to find the direction of any leaks

Sent from my SM-A426U using Tapatalk

 

[MidnightMoon]

It's either a vacuum leak or the pump. You really need a gauge to tell if it is good or not.

You can also block off the ports on the vacuum manifold to find the direction of any leaks

Sent from my SM-A426U using Tapatalk

How often does the vacuum manifold go out? I know that's probably not it but it is also an old truck. I am the second owner of it and it was 99% original. Ford everything on there except the hubs so the old guy took real good care of her. But do I just disconnect a area of the vacuum manifold and if it starts working when I block it off thats it?

 

[Bugman]

The manifold usually doesn't go out, but as old as our trucks are the vacuum lines start to get old and brittle. You don't say if you have a 4x4 with automatic hubs but that is one place that starts to leak. To block off ports you will need to pick up some caps at the parts store that will fit over the nipples off of the manifold to block off that line.

Another way to test to see if you don't have enough vacuum is to set your HVAC to AC or where the air is blowing out of the vents. Then hold the brake pedal down and see if the air switches to the defrost vents. The defrost vents are the default position for the air flow. So if it switches you don't have enough vacuum for all that you need it for.

 

[MidnightMoon]

The manifold usually doesn't go out, but as old as our trucks are the vacuum lines start to get old and brittle. You don't say if you have a 4x4 with automatic hubs but that is one place that starts to leak. To block off ports you will need to pick up some caps at the parts store that will fit over the nipples off of the manifold to block off that line.

Another way to test to see if you don't have enough vacuum is to set your HVAC to AC or where the air is blowing out of the vents. Then hold the brake pedal down and see if the air switches to the defrost vents. The defrost vents are the default position for the air flow. So if it switches you don't have enough vacuum for all that you need it for.

It already has Manuel hubs on it. That was the only thing i forgot was not ford haha. So those are already gone

 

[1970something]

my bet is the vacuum pump is shot.
with china junk these days pumps are only good for three -five years unlike the 15-20 years of the old USA made pumps.

the give away is one good brake application and than hard.
than if you wait a few minutes you get one good application again.

 

[Hendy]

I have the manual for the vacuum lines, It'll probably take me about 30 minutes but I'll try to find the diagrams you're looking for

 

[Hendy]

Also Welcome to PSN
We are glad to have you here

 

[PowerStrokeMeF450]

I've been seeing a lot of defective boosters these days at my shop. Just saying, could be a defective new part.

 

[Hendy]

Here's what I've found

 

[MidnightMoon]

my bet is the vacuum pump is shot.
with china junk these days pumps are only good for three -five years unlike the 15-20 years of the old USA made pumps.

the give away is one good brake application and than hard.
than if you wait a few minutes you get one good application again.

Yeah I figured it would either be that or a vacuum leak. I assumed vacuum leak because I have vacuum at the check valve on the booster but i wanted to rule other things out before i spent the money

 

[1970something]

problem with that line of thought is, if you have vacuum leaks, you would not have enough vacuum to work the booster.

 

[scottu5]

I had the exact same problem a few years back (hard pedal after one application).

It was the vacuum pump, which had been replaced (new), only a year earlier.

 

[scottu5]

I had the exact same problem a few years back (hard pedal after one application).

It was the vacuum pump, which had been replaced (new), only a year earlier.

I went back and found my old post…it was a little over 2 years ago and the replacement was a ‘reman’, (not new) and failed after 60k miles (not one year)..everything else was correct (so much for my memory🤣…but it was a bad vacuum pump.

 

[rlbfalcon]

I just finished fixing my 97 F250HD 7.3 brake issue. mine had the brake light on until it got up to operating temp. I pulled the vacuum line from that goes from the vacuum pump to the distribution 4 port distribution center at the distribution center end. I checked the vacuum and found it to be correct (approx 18 in hg). Thought I was home free But when I moved the hose the vacuum dropped significantly. the hose was leaking at the vacuum pump port. I replaced the hose and put a hose clamp on it. I went ahead and replaced all my vacuum hose. Problem resolved.

 

[Hendy]

I have the manual for the vacuum lines, It'll probably take me about 30 minutes but I'll try to find the diagrams you're looking for

Why'd you copy my message 😂
also welcome to PSN

 

[1970something]

Why'd you copy my message 😂
also welcome to PSN

spammer from india

 

[Hendy]

That would make sense